The present invention relates to methods of forming hollow, porous elastomeric bodies and hollow, duo-layered elastomeric bodies wherein one layer is porous and continuous with the other layer which is solid.
In the medical field, it has been suggested that it is advantageous for some applications to use implantable polymer-based devices having porous surfaces. For example, it has been suggested that vascular prostheses having porous surfaces on the inside aid in keeping blood clots on the surface of the vascular prosthesis and reduce the chances of having the clots break off the vascular wall, enter the bloodstream, and embolize to various parts of the body. It has also been suggested that having a porous outer surface on mammary prostheses reduces the chances of capsular contracture.
Various patents disclose methods of making porous polymeric bodies. For example, U.S. Pat. Nos. 4,604,762 and 4,459,252 disclose methods for forming porous-surfaced prostheses by mixing salt particles or other water-elutable material with an elastomeric composition, allowing the composition to harden, and removing the water-elutable material by leaching with water.
U.S. Pat. No. 4,199,864 discloses a method of fabricating a plastic implant having a porous surface by coating a mold interior with a release agent, sprinkling a layer of water-soluble crystals on the coated surface, adding an acrylic polymer and monomer mixture to fill the mold, heat curing the mixture, and, subsequently, removing the water soluble crystals by leaching. Examples of the release agent are given as mineral oil and a release agent "sold under the name `Mar-va-foil`".
U.S. Pat. No. 3,700,380 discloses a method of forming blood handling prostheses containing microcavities by applying fibrous, particulate, or granular material such as NaCl crystals to the surface which is to contain microcavities, while the surface is soft, causing the surface to set up, and thereafter using a solvent which dissolves the particles.